Seems like alot of folks are asking for more functionality out of the stereo headphone capability than Handspring was expecting.

I need to preface this blurb with a quick disclaimer. My theory of how the Treo uses the audio accessory jack is speculation.

But I think the way T600s are using the audio accessory jack, they're going to have to actually issue OS and application updates to allow the jack to operate the way we all would like. In particular, they will need to update the controller for the audio accessory jack, perference settings, and possibly apps that have to make a decision on whether to output stereo signal, or mono+mic (apps like Phone, and P-Tunes).

Everything I've seen to date tells me that the way they've worked it out, the T600 actually tries to detect whether you have a headset, or a pair of headphones on, by measuring some signal from the mic pole. If it thinks the accessory resembles a headset, it will map functionality to the accessory jack accordingly (monospeaker signal, mic signal, and ground). If it thinks the accessory resembles characteristics of a pair of headphones, it will map functionality to the accessory jack accordingly (Leftspeaker, right speaker, Ground) In this second scenario the now-missing mic functionality is then re-mapped to receive the mic signal from the built-in mic on the back of the device. This way, it offers a nice hands-free type of arrangement that does not require special 3rd party product development. The mic works surprisingly well at picking up voice from 3-4' away too.

The thing is, I don't think they foresaw this demand for stereo headphone functionality AND an accessory mic. It doesn't work that way now. You cannot run 4 signals through a 3-pole jack. And to operate STEREO headphones AND an Accessory mic, you're going to need 1) A left speaker signal, 2) a right speaker signal, 3) a mic signal, 4) a ground signal. Add it up, and you have one too many signals for a 3-pole jack. You need a 4-pole jack. Either that, or you need some fancy software coding. It was designed, I believe, with the requirement that it work with standard stereo headphones, not some fancy custom headphone for which people have to pay more bucks. It's a fair assumption that they would make. They got alot of flack for using a funny 4-pole arrangement last time. And they must've felt pretty clever about retasking the mic pole with software, rather than forcing folks to go to 4-pole and custom equipment. After all, given the widespread standard of a mono headset/mic products with 3-pole jacks, and coincidentally, stereo headphones and similar 3-pole jacks, this arrangement provides good functionality, reacts fairly intuitively, and does not require conversion between 3-pole and 4-pole configurations to provide compatibility with standard stereo headphones. The trick they do with the re-mapping of the poles...that almost gets you there. But it's not as intelligent as we would like it to be.

Now...we're saying we want it. And to get it, we're going to need HS to stop the T600 from trying to auto-sense the accessory.

If they simply provide a little set of radio buttons for us to check off in the preferences app, indicating "I am using a: 1) Stereo Headset+Mic ; 2) Standard Stereo Headphones, or 3) Standard Monoaudio+Mic Headset" they could begin to solve our problem.

When checked with the Stereo Headset+Mic option, the T600 now has to dynamically switch between sending stereo audio signals through the accessory jack, vs. mono audio and mic signals. Any application that requires the use of the mic triggers the T600 to map the mic to the accessory jack, rather than the built-in jack, and a mono audio signal. This would include the PHONE app, as well as, for example, a third-party voice recording app. In this condition, audio signals would come through the as a mono signal, and be sent to only one headphone speaker. The other channel is being used by the mic, and can't drive the other speaker. You'd only hear out of one ear. But the mic works, and the headphone vendor could make one that plays mono out of both ears with the flick of a switch, or auto detects. The other preference settings HS already has down. It's this 3rd setting that's tricky.

Originally posted by djs_tx All the smart software in the world will not let you use a single conductor as a simultaneous bi-directional line. Electrons can only go in one direction at once.

The best you could possible do is have it switch so fast between input and output that you don't notice its doing two things at once. But I guarantee you the hardware to that speed of switching ain't there.
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You're right, I doubt they can give us a TOTALLY dynamic switching betwen sending mic signals and stereo audio signals on the fly. That would be neat, and totally seamless. But you're right, that I think can only feasibly be done by the 4-pole option.

But if we acquiesce to the idea that you can task the mic pole to be application specific, then it would only have to re-map the poles as the applications change. When it switches from an MP3 playing app to a voice recording app...BAM, Switch. When you're done with the voice recording app, and start up the MP3 app again, bam...switch back.

A preference screen like this one, would work hand in hand with apps that specify what input/output it has. The t600 then will know whether it will have a mic signal to send, or a stereo signal. If the Stereo Headset+mic setting is selected, and the app has a mic signal, then it'll choose to send the mic signal to the audio accessory jack.

What you really want is a "smart headset". Headphones that could sense whether the shared pole is an input or an output.

You plug the headset in and start your music application. When an incoming call occurs, the treo sends some signal to the headset and it pauses your music, reconfigures to route the mono incoming sound to both ears and routes the mic signal to the shared pole. When the call is over it reconfigures back to playing stereo music again. I think what I just described is possible with a soldering iron and a radio shack catalog (except for auto pausing the music).

Your headset would have to have a battery and some simple logic circuitry. As much attention as Handspring pays to the user interface, I bet they will eventually release some hardware to do this with a simple enabling software.

Originally posted by rekadau I would just like to know why the Treo300 had a four pole jack and no stereo. Now that they have stereo on the 600 they go to a three pole jack. It just makes no sense to me.

I know what you mean. It seems kinda goofy, doesn't it?

You know, when it comes to product development in this arena, you get alot of interesting perspectives...particularly at the confluence of converging applications. You have here the confluence of the cell phone standards (a combination of 3 & 4 pole standards) vs. audio playback standards like MP3 players (solely 3-pole standard), and such.

Product development has to make judgement calls on when to adopt standards and mold product specs around that standard, versus when to push for an evolution of standards and build the new standards around a new paradigm of functionality. In this particular case, with the possibility of a 512mb SD Card (soon to be 1Gb), suddenly, it becomes a debatable question of whether to adopt MP3 player standards and try to conform to a 3-pole design or not. I suspect they really wrangled with this one, because of the drawbacks in functionality.

The problem is that it really *is* difficult to get a new standard to be adopted enthusiastically. It's much easier to say "hey...get this dinky $15 readily available adaptor, and you can use your existing standard headphones, which we know you have a gazilliion of, because you were never satisfied with any of them!" versus saying "hey, buy this $80 fancy schnancy headphone with a mic, and 4 jacks," and then pusing specs out to accessory vendors, hoping some company actually makes something cool enough. With the 3-pole direction, and that creative mic-pole mapping that they did, they at least know that the standard coincides with both segment's expectations.

I'm not too surprised HS took this approach, really. I get the impression that HS is pretty selective on what standards they intend to make a big deal about, and how quickly they push it. They made a splash with the graffiti standard...but took a long time to move away from the up/down navigator to the 5-direction navigator, waiting for quite a large imbedded base of cell-phone users who would welcome the functionality in the converged device. In fact, I get the sense that HS has definitely shifted their strategy these days from one of standards-leading design, to one of standards-converging design.

Personally, I really think they should've pushed for a 4-pole solution, since an adapter is still required for standard 1/8" headphone jacks anyways. If I were in their shoes, the issue I would have had with that is that there will *still* be a need to let people use standard stereo headphones with the device, and 1/8" 3-pole to 2.5mm 3-pole adapters are readily available. Whereas 1/8" 3-pole adapters to 2.5mm 4-pole adapters with a particular mapping of poles has not yet been done.

I know of at least one other product out there--the Nokia N-Gage--which actually have *two* headphone jacks--one for stereo, and one for the mono/mic, which I also think indicates a resistance to actually push the two standards together. Skullcandy exists solely because the two standards have yet to be merged into one. BTW, if I were at the helm of Skullcandy, I would be working those business development relationships like MAD, to get ahead of the curve and put out the best damn converged systems on the planet...)

I would suspect that once the market really adopts a unified device, they're going to roll out the Treo 650 and wow us with more and more integration. bluetooth integration...better camera...full-stereo+mic support...oh those bastards!